Second time new phone goes in for repairs

I am very up set.my new phone heated up i send it to the repairs they said they fixed it.i got it back still doing the same thing. A guy phoned me said i must book it in again but they will try for a spesial obf. I called the assistant manager at heidelberg mall vodacom chantel shee said i should go to another vodacom se refuses to help me when i phoned she put the phone down in my ear twice. Now nobody knows anything about the special obf. And i am paying for a new phone thata being fixed 2 times.i have been a contract customer for 10 years.but dont like this service from a assistant manager.